[0001] This invention relates to a novel pressure independent control valve.
[0002] Pressure independent control valves are known. Typically such valves are with a mechanism
to enhance control of fluid flow independently of system pressure. Such valves may
be employed with a differential pressure controller and are commonly used in heating
ventilation and cooling systems.
[0003] Conventional pressure independent control valves comprise a globe valve incoporating
a plug which is actuated by a linear actuator. Since the actuator typically is operated
through a wall of the valve housing, it is usual for the plug to travel at an angle
(typically 60 to 90 degrees) to the axis of the housing and direction of flow of fluid
through the conduit into which the valve is installed.
[0004] In accordance with the present invention there is provided a control valve comprising;
a wall defining a chamber, the chamber having an inlet end a middle portion and an
outlet end in axial alignment, a valve seat and a valve plug proportioned to fit the
valve seat arranged in axial alignment within the chamber and at least one of the
valve seat and valve plug configured for axial movement towards the other, relative
movement between the valve plug and valve seat being enabled by means of a cam mechanism
comprising, a first shaft assembly extending axially along the chamber and fixed to
one of the valve plug and vlave seat, a cam operable with the first shaft assembly
to separate or draw together the valve seat and valve plug along the axis of the chamber,
a second shaft assembly coupled to the cam and extending through the middle portion
of the chamber wall terminating in a free end, the free end being configured for attachment
to a rotary actuator.
[0005] In use, rotary actuation of the second shaft assembly is translated, via the cam,
to linear actuation of the first shaft assembly which in turn effects linear motion
of the plug or seat axially of the chamber.
[0006] Preferably, the cam and shaft assembly arrangement is confrigured to be operable
to move the valve seat towards the valve plug, the valve plug being fixed in position.
[0007] The assembly may further comprise a stroke limitation mechanism.
[0008] Desirably, the first and second shaft assemblies are arranged to be perpendicular
to one another.
[0009] The pressure independent control valve can conveniently be used in combination with
an inline differential pressure controller. In a preferred embodiment, the inline
differential pressure controller sits downstream of the pressure independent control
valve of the invention in line with the control valve and comprises a wall defining
a chamber, the chamber having an inlet end and an outlet end in axial alignment; a
valve seat and a valve plug proportioned to fit the valve seat arranged in axial alignment
within the chamber and at least one of the valve seat and valve plug configured for
axial movement towards the other when a pre-defined load from the inlet end is exceeded
whereby to close the valve, resilient means for resisting the axial movement when
the pre-defined load is not exceeded and a pilot valve integrated into the wall of
the chamber and in fluid communication with the chamber by means of one or more conduits
provided within the chamber wall.
[0010] The inline differential pressure controller may comprise various optional features
as set out in the Applicant's co-pending patent application filed the same date as
this patent application and repeated here.
[0011] A further objective is to provide a user friendly adjustment means involving a simple
low torque setting of a pilot valve and ease of the pilot valve change over.
[0012] In a particular embodiment, the valve seat is operated by an annular diaphragm positioned
proximal to the inlet end and carried on the annular valve seat which extends distally
and is arranged for axial movement towards the outlet end; the resilient means is
a coiled spring arranged for resisting said axial movement of the annular diaphragm
and valve seat and the valve plug is fixedly mounted proximal to the outlet end and
in axial alignment with the annular diaphragm and valve seat. The spring characteristics
match the pre-defined load.
[0013] The pilot valve is of conventional construction. The walls of the main valve chamber
are prepared to receive the pilot valve by providing a recess in the wall proportioned
to receive the pilot valve and incorporating pressure signal conduits (or impulse
pipes) to connect the pilot valve with the chamber of the main valve through drillings
defining channels and conduits in the chamber wall. Conveniently, the recess and pilot
valve body may be provided with complementing screw threads to allow easy and secure
installation of the pilot valve whilst maintaining ease of removal or replacement
of the pilot valve when repairing / maintaining the controller.
[0014] Various modifications to the design can be envisaged without departing from the invention.
For example, the valve may be arranged for the plug to move towards the seat and resilient
means other than a coil spring may be employed to balance the movement of the valve
plug.
[0015] It will be appreciated that flow through a valve is dependent on the valve opening
and differential pressures applied to the valve. Pressures in a hydronic system to
which the invention is suitably applied can vary a lot and can cause control problems.
In order to make the valve operation independent of pressure variation such that the
flow depends only on the opening and closing of the control valve, it is necessary
to keep the differential pressure across the control valve as constant as possible.
This can be achieved by adding a differential pressure controller to the valve or
rather into a common valve body as further described below.
[0016] The valves of the invention offer many advantages over conventional designs; the
hydronic resistance of the inline valve geometry is relatively low compared with conventional
globe valve geometry, as a consequence the inline valve of the invention can be made
smaller. Smaller valve size provides benefits in manufacture in the form of lower
material, storage and transport costs, benefits for the installer as the smaller valves
are easier to manipulate during installation and benefits to the end-user as the valves
take up less space when installed.
[0017] Other more technical advantages are that noise characteristics of the inline valve
arrangement are better than conventionally used valve configurations, i.e they are
more quite in operation. Furthermore, the cam operation of the valve seat has been
found to produce high valve performance characteristics that can be further optimized
by changing geometry of only one relatively simple part of the valve.
[0018] One embodiment of the invention will now be further described by way of example with
reference to the following figures in which:
Figure 1 shows an embodiment of a pressure independent control valve in accordance
with the invention embodied in a single valve body which also includes a stroke limitation
mechanism and differential pressure controller in line with the pressure independent
control valve. The valve body is shown in cross section through a first axis.
Figure 2 shows the embodiment of Figure 1 in cross section through a second axis of
the valve body, through a plane perpendicular to the first axis.
[0019] As can be seen from the Figures, the valve body consists of a wall defining an inlet
chamber (8), a middle chamber (48) and an outlet chamber (46), assembled together
by number of fasteners (22, 33), for example screws or bolts, placed along flanges
on all three chambers. The inlet and outlet chambers (8, 46) have blind holes with
threads that are used for installing the valve between flanges on a target pipeline.
Chambers provided in the valve body include various drillings to provide conduits
that enable pressures to be transmitted to various points inside the valve chamber
and for venting of chambers and installing pressure test points.
[0020] An inline control valve is installed between the inlet chamber (8) and the middle
chamber (48). The inline control valve consists of a fixed control valve seat (16)
fastened into the inlet chamber (8), and a valve plug, that consists of a control
element (4), a fixed cover (21), a pressure relieved control cylinder (20), a seal
(19), a cover (11) and a cam mechanism (described in more detail below). Control element
(4) is held in place by a ring (3) that is fixed to the middle chamber by number of
screws or other fasteners (23).
[0021] The cam mechanism consists of a first, inline shaft assembly (14, 15, 28), a cam
(24), bearings (51, 52) and a second, perpendicular shaft (2). The inline shaft is
sealed by the lip-seal (12) which prevents water from entering the control element
(4). Movement of the inline shaft assembly (14, 15, 28) is guided by a guide (29)
and a fixed cover (21). An end of the perpendicular shaft (2) protrudes outside the
middle chamber wall (48), the end is shaped so that a rotational actuator (50) can
be operably connected to it. Rotation of the actuator (50) in turn rotates the perpendicular
shaft (2) and this motion is transferred, via the cam, into an inline displacement
of inline shaft assembly (14, 15, 28), Since the control cylinder (20), cover (11)
and inline shaft assembly (14, 15, 28) are fixed together by a number of screws (10,
13), they move together in an axial direction along the valve chamber opening and
closing the gap between control valve seat (16) and cover (11) as required thereby
controlling the flow of fluid through the control valve.
[0022] Between the actuator (50) and the perpendicular shaft (2) is shown an optional stroke
limitation mechanism (49). By turning the adjustment screw one can limit the angle
of actuator movement. This way also the stroke of the inline shaft assembly (14, 15,
28) is limited, and thus the opening of the control valve is limited.
[0023] Downstream of the control valve there is an inline differential pressure controller.
Centred inside the outlet chamber (46) there is star shaped valve plug, which consists
of a differential star (44), a seal (42) and a cover (43) assembled together by number
of screws (45). The star is held in place by a ring (39) that is fixed to the outlet
chamber by a number of screws (40)
[0024] Inside the middle chamber (48) there is a ring shaped diaphragm (32). The outer edge
of the diaphragm (32) is fixed to the middle chamber by a diaphragm ring (31) and
a plurality of screws (47), while the inner edge is fixed to the middle chamber by
a funnel (35).
[0025] Between the middle chamber and outlet chamber there is a differential valve seat
(41) that is screwed into a disc (34). Together, in use, they move in an inline (axial)
direction under influence of differential pressure on the diaphragm and the force
of springs (36, 37). Moving parts are guided by the funnel (35) and guide (38)
[0026] As shown in the Figures, pressure (p1) upstream of the control valve is transmitted
through drilled channels in inlet chamber (8) and middle chamber (46) to the inlet
side of the diaphragm (32) and acts in favour of closing the valve. Pressure (p2)
downstream of the control valve is transmitted through drilled channels in the disc
(34) to the outlet side of the diaphragm (32) and together with the force of springs
(36, 37) acts in favour of opening the valve. As long as the differential pressure
(the difference of pressures p1 - p2), multiplied by the active surface area of the
diaphragm is equal to the spring force, the valve remains stationary. If the differential
pressure increases, the differential pressure control valve closes (and vice versa).
Thus the differential pressure across the control valve is kept almost constant.
1. A control valve comprising; a wall defining a chamber, the chamber having an inlet
end (8) a middle portion (48) and an outlet end (46) in axial alignment, a valve seat
(16) and a valve plug (4, 21, 20, 19, 11) proportioned to fit the valve seat (16)
arranged in axial alignment within the chamber and at least one of the valve seat
(16) and valve plug (4, 21, 20, 19, 11) configured for axial movement towards the
other, relative movement between the valve plug and valve seat being enabled by means
of a cam mechanism comprising, a first shaft assembly (14, 15, 28) extending axially
along the chamber and fixed to one of the valve plug (4, 21, 20, 19, 11) and vlave
seat (16), a cam (24) operable with the first shaft assembly (14, 15, 28) to separate
or draw together the valve seat and valve plug along the axis of the chamber, a second
shaft assembly (2) coupled to the cam (24) and extending through the middle portion
(48) of the chamber wall terminating in a free end, the free end being configured
for attachment to a rotary actuator (50).
2. A control valve as claimed in claim 1 wherein the cam (24) and shaft assembly arrangement
(14, 15, 28; 2) are confrigured to be operable to move the valve seat (16) towards
the valve plug (4, 21, 20, 19, 11), the valve plug being fixed in position.
3. A control valve as claimed in claim 1 or claim 2 wherein the assembly further comprises
a stroke limitation mechanism (49).
4. A control valve as claimed in any preceding claim wherein the first and second shaft
assemblies (14, 15, 28; 2) are arranged to be perpendicular to one another.
5. A pressure independent control valve comprising a valve body housing a control valve
in accordance with any preceding claim in combination with an inline differential
pressure controller (31,...,47).
6. A pressure independent control valve as claimed in claim 5 wherein the inline differential
pressure controller sits downstream of the pressure independent control valve of the
invention in line with the control valve and comprises a wall defining a chamber (48),
the chamber having an inlet end and an outlet end (46) in axial alignment; a valve
seat (41)and a valve plug (42, 43, 44) proportioned to fit the valve seat (41) arranged
in axial alignment within the chamber and at least one of the valve seat and valve
plug configured for axial movement towards the other when a pre-defined load from
the inlet end is exceeded whereby to close the valve and resilient means (36, 37)
for resisting the axial movement when the pre-defined load is not exceeded.
7. A pressure independent control valve as claimed in claim 6 further comprising a pilot
valve integrated into the wall of the chamber and in fluid communication with the
chamber by means of one or more conduits provided within the chamber wall.
8. A pressure independent control valve as claimed in claim 6 or 7 wherein the valve
seat (41) is operated by an annular diaphragm (31) positioned proximal to the inlet
end and carried on the annular valve seat (41) which extends distally and is arranged
for axial movement towards the outlet end (46); the resilient means (36, 37) is a
coiled spring arranged for resisting said axial movement of the annular diaphragm
(31) and valve seat (41) and the valve plug (42, 43, 44) is fixedly mounted proximal
to the outlet end and in axial alignment with the annular diaphragm (31) and valve
seat (41) and wherein the spring characteristics match the pre-defined load.
9. A pipe fitted with a pressure independent control valve as claimed in any of claims
5 to 8.
10. A hydronic system including a return pipe as claimed in claim 9.